Simple Model Cell is Key to Understanding Cell Complexity

The model cell developed in the lab of Christine D. Keating at Penn State uses as the cytoplasm a solution of two different polymers, PEG and dextran (Panel A). The image in Panel B is the image in Panel A highlighted with fluorescent dyes. The blue region is PEG, which is concentrated in the outer polymer solution; the green area is the portion of the membrane that contains PEG groups, which interact with the contents of the cell; and the red area is the portion of the membrane with fewer PEG groups, which interact with the contents of the cell to a lesser extent. After exposure to a concentrated solution of sugar, the cell converted to a budded form (Panel C). A dextran-rich mixture filled the bud, while a PEG-rich mixture remained inside the body of the cell. Panel D shows the image in Panel C highlighted with fluorescent dyes. The blue area is the PEG-rich region. This new structure exhibits polarity both in the membrane and in the aqueous interior of the model cell. Credit: Christine D. Keating lab, Penn State